Not a safe assumption. OH 4 is a chance for breaking changes. There can be huge changes from one snapshot to the next right now. Just as an example, OH M1 eliminated JS as a transform, using SCRIPT instead. As of M2, JS is back and SCRIPT is gone.
RULE_ID? Your .items files are in the items folder and not rules, right?
If so, report this on the milestone thread. openHAB 4.0 Milestone discussion - #194 by Andrew_Rowe